Debt and Credit Arrangements Debt Transactions (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Gain (Loss) on Extinguishment of Debt	$ (74,000,000.0)	$ 0.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	(5,200,000)	$ (600,000)
4.750% Notes Due 2030 (less unamortized discount and issuance costs of $3.5 and $5.5, respectively)
Debt Instrument [Line Items]
Par Value	$ 650,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	4.75%
4.000% Notes Due 2022
Debt Instrument [Line Items]
Par Value	$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Gain (Loss) on Extinguishment of Debt	$ 9,200,000
Redemption Premium	8,600,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	600,000
Payment for Debt Extinguishment or Debt Prepayment Cost	258,900,000
4.200% Notes Due 2024 (less unamortized discount and issuance costs of $0.2 and $0.6, respectively)
Debt Instrument [Line Items]
Par Value	500,000,000.0
Unsecured Debt 3.75% Note Due in 2021 [Member]
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Unsecured Debt 2.400% Note [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.40%
Unsecured Debt	$ 494,500,000
Debt Instrument, Unamortized Discount	800,000
Debt Issuance Costs, Gross	4,700,000
Unsecured Debt 4.65% Notes [Member]
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	4.65%
Unsecured Debt 5.40% Notes [Member]
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	5.40%
2.400% Notes Due 2031 (less unamortized discount and issuance costs of $0.8 and $4.7, respectively)
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
3.750% Notes Due 2023
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Gain (Loss) on Extinguishment of Debt	$ 36,500,000
Redemption Premium	30,700,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	1,100,000
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	4,700,000
Payment for Debt Extinguishment or Debt Prepayment Cost	532,900,000
Unsecured Debt 3.375% Note
Debt Instrument [Line Items]
Par Value	$ 500,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	3.375%
Unsecured Debt	$ 493,100,000
Debt Instrument, Unamortized Discount	1,100,000
Debt Issuance Costs, Gross	5,800,000
Unsecured Debt 4.200% Notes Remaining Principal
Debt Instrument [Line Items]
Par Value	$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage	4.20%
Gain (Loss) on Extinguishment of Debt	$ 28,300,000
Redemption Premium	27,500,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	800,000
Payment for Debt Extinguishment or Debt Prepayment Cost	$ 282,200,000

Face (par) amount of debt instrument at time of issuance.

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